This invention is directed to a turbine for power generation, and in particular, a miniature turbine capable of operation in a vacuum.
The current trend towards miniaturization, portability and more in general ubiquitous intelligence, has led to the development of a wide range of new portable powered products such as laptops, cellular phones, PDAs, etc. However, the power requirements of such systems have received much less attention: typically, traditional battery-operated electronic systems are used. Nevertheless, the energy density of most fueled power units are still one hundred times more than that of the best performing batteries. Such power units can be based on a wide range of operating principles, ranging from fuel cells and thermoelectric devices, to combustion engines and gas turbines.
While fuel cells are expected to offer the highest efficiency, micro gas turbines are expected to offer the highest power density. Given the need for mobile high power density, energy conversion needs to be provided in very small packages. One such prior art solution, the Brayton power cycle (gas turbine) is superior based on considerations of power density, simplicity of manufacture, and efficiency.
The Brayton gas turbine consists of a compressor, a combustion chamber, and a turbine driven by the combustion exhaust that powers the compressor. A macro-scale gas turbine with a meter-diameter air intake area generates power on the order of 100 MW. The residual enthalpy in the exhaust stream provides thrust or can power an electric generator. Therefore, a micro-scale gas turbine generator with the same basic architecture would produce tens of watts of power as long as the power per unit air flow is maintained. However, the current Brayton turbines suffer from the disadvantage that they require large venting compressors to make use of environmental air, and do not readily lend themselves to miniaturization, or work in all environments. They are also energy inefficient. Accordingly, a gas turbine generator which overcomes the shortcomings of the prior art is desired.